As used in specification, permanent setting of the hair refers to the process of chemically treating the hair whereby the breaking down and reformation of covalent bonds in the hair causes the structure of the hair to be altered. Permanent setting is used to create waves, curls and the like in the hair on a "permanent" basis.
A distinction may be made between the processes of permanent setting and that of cohesive setting in that in the latter case, the hair is merely heated in a wet state, without any chemical action, until the hair is substantially dry. A cohesive set whilst also able to produce wave or curled hair lacks permanency due to the fact that as soon as the cohesively set hair is wet, the curl or wave is lost. Such wetting as that caused by excessive ambient humidity or washing is sufficient to defeat a cohesive set.
By contrast, a permanent set is unaffected by the presence of water to the extent that even after washing, the hair will be maintained in its curled or waved state..
It is well known in the art that a permanent set may be achieved by the treatment of the hair using various compositions, typically aqueous thioglycollate solutions such as those based on ammonium thioglycollate, under neutral or alkaline condition. Typically, the hair to be set is wet with the thioglycollate solution and then wound onto curling or perming rods. The hair is then left for up to about thirty minutes after which time the hair is treated with a neutralizer solution, the curlers removed. and the so treated hair washed to remove substantially all of the chemicals used in the treatment. It is to be noted that the purpose of the neutralizer solution is to terminate the reaction of the thioglycollate with the hair.
Although the aforementioned process has been known for some time, it would appear that there have been relatively few changes made thereto, although it is to be noted that there have been numerous modifications proposed to the setting composition.
One of the disadvantages of the process is the time taken to effect setting and the attended discomfort the person whose hair is being set experiences in setting. To this end, the prior art has recognized that the rate of reaction of setting compositions on the hair may be increased by heating. Unfortunately, without very close control of the heating conditions, the effect of the application of heat on the process has been found to be generally too variable with the result that the quality of the setting obtained is usually unacceptable.
In PCT/EP82/00173 (WO83/00606) there is disclosed heat treatment apparatus for heating the human hair on the head which uses an infrared source to generate heat in the hair. This apparatus is disclosed as being useful in the permanent setting of the hair. However, it is to be noted that this apparatus generates and applies infrared radiation from a source external to the hair.
In other art such as Australian patent 514,434, there are disclosed infrared hair dryers. In this patent and the other art known to the present applicant, such apparatus utilise infrared radiation sources external to the hair generally in conjunction with blowers to dry the hair. Clearly the infrared sources in these apparatus are used merely as a source of heat, ambient air being drawn over the sources, heated and blown onto the hair.
U.S. Pat. No. 4,602,143 (Mack et al) discloses an apparatus for use in cohesive hair setting in which moistened hair is wound on a member in which there is disposed an infrared radiation source. By controlling the duration of action of the source, the extent of heating can be controlled to effect drying of the hair rapidly, whilst the cohesive set is formed.
The present inventor has recognized that there continues to exist a need for an apparatus and a method by which the hair may be set quickly, reliably, reproducibly and permanently, that is a set not lost in water or high humidities.